南海沉积物总量的统计:方法与结果

The Statistics of Sediment Mass in the South China Sea: Method and Result

通过收集包括大洋钻探钻井岩芯在内的大量地质地球物理资料,获得了南海的沉积物厚度分布格局,并统计了自渐新世以来的沉积总量以及E3、N11、N21、N31、N2、Q各时期的沉积量。结果表明,在前渐新世基底之上,南海海盆中共有7.01×106km3的沉积物,总质量为1.44×1016吨。以渐新世33 Ma的年龄计,南海的平均堆积速率是12.8 g/(cm2.ka)。南海沉积物主要堆积在陆架和陆坡上,中央海盆的沉积总量不及全部的5%。陆架和陆坡上发育的沉积盆地,如果以沉积厚度2km为边界,则只占南海总面积的34%,却堆积了南海沉积总量的82%,表明沉积盆地是南海接受沉积物的主体。晚渐新世是南海沉积量最大、堆积速率最高的时期,与全球沉积速率演变有明显差异,显示出边缘海盆地的沉积作用,首先受该地构造作用的控制。

Based on a great deal of geological and geophysical data including ODP borehole data in the South China Sea （ SCS）, the figures of sediment pattern were developed and the mass volume was calculated both of the whole basin and during each stage of E3, N1^1、N1^2、N1^3、N2, Q. Above the pre-Oligocene base, the sediment volume of SCS was 7.01 ×10^6km^3 and the mass was 1.44 ×10^16 t, and the average sediment rate was 6.22 cm/ka and accumulation rate was 12.8 g/cm^2/ka since Oligocene. Most of the sediment deposited on the continent shelf and slope, while only 5% of total mass deposited in the Center Basin. The sediment basin, developed in the continent shelf and slope, occupied 34% of the whole area of SCS given the thickness contour 2000 m as the boundary, but more than 82% of total amount mass deposited in these basin, showing that sediment basin was the major part of sedimentary process in SCS. The sediment rates were the highest and the mass volume was the largest in SCS during Oligocene, which was quite different from the evolution of global sediment rates, and it can be concluded that the deposition of marginal seas is controlled by the local tectonic movement firstly.